On Sept. 16, they open the second edition of the Chicago Architecture Biennial as its artistic directors. Featuring work from more than 140 architects and designers around the world, the Biennial is expected to draw some 500,000 visitors. Across town that same week, Ms. Johnston and Mr. Lee, who are married, also unveil Phase 1 of their renovation of Josef Paul Kleihues’s Museum of Contemporary Art, an attempt to humanize the famously aloof building by unlocking some of its unyielding geometry and embracing the park to its east.

Image

Rendering of the Menil Drawing Institute, designed by Johnston Marklee as a new wing for the Menil Collection in Houston.CreditJohnston Marklee/Nephew

And about two months later, when their 30,000-square-foot Menil Drawing Institute finishes construction (the building will open next spring), Johnston Marklee will add a new wing to Houston’s renowned Menil Collection. (Neither the Drawing Institute nor Renzo Piano’s main building for the Menil, which opened to great fanfare in 1987, were damaged during Hurricane Harvey.) The Drawing Institute extends Mr. Piano’s restrained visual language with a cluster of pavilions that define three new courtyards. Pleated ceilings activate the interiors, and attenuate Houston’s abundant daylight.

Ms. Johnston, 51, and Mr. Lee, 49, are part of a bumper crop of designers whose sensibilities are bringing new depth to contemporary architecture around the world.

In architecture, where buildings germinate slowly and early commissions tend to be small, Ms. Johnston and Mr. Lee are still young. But after 20 years of practice, they’re seasoned enough for clients like the Menil to entrust them with significant commissions. They are in that fertile period — agewise, it typically runs from the mid-40s to mid-50s in architecture — when the profession’s next generation of leadership begins to make its mark. Mr. Piano was 50 when the Menil, his American debut, opened. It was only after the renovation of his house, at 48, that Mr. Gehry became architecture’s other important Frank. Zaha Hadid was mostly an academic architect well into her 40s.

In 2018, when they complete Rome’s Città del Sole (City of the Sun), Maria Claudia Clemente, 50, and Francesco Isidori, 47, partners of that city’s Labics studio, will have been at work on the complex for most of the time they’ve practiced together. Won in a 2007 competition, the 175,000-square-foot project comprises a library and residential, office, retail, parking and extensive public space — a critical component of Roman urban life. The sleek urban center replaces a derelict former bus depot and repair yard hidden behind fences along Rome’s eastern edge. “But our goal was not to build a collection of interesting architectural objects,” Ms. Clemente and Mr. Isidori said. “We wanted to create a coherent structural tissue for this part of the city.”

Some 5,500 miles east of Rome, Gong Dong, the 45-year-old founder of Vector Architects in Beijing, has transformed another industrial relic into a contemporary retreat. His just-opened, 117-room Alila Yangshuo Hotel encompasses a former sugar refinery located along the banks of the Li River in Guilin. Though the refinery, a 1950s business, didn’t survive Deng Xiaoping’s economic modernization drive, its building did. Chinese investors, inspired by the picturesque location — its dramatic karst topography and lush growth have been the source of countless Chinese landscape paintings — approached the architect with the idea of a resort hotel.

For Mr. Gong, the client’s interest in repurposing the original building reflects a renewed Chinese appreciation for cultural preservation. “Our society is rethinking what we’ve been doing over the last 20 years — this rapid urbanization at the cost of all else,” he said. “There is a new interest in quality, and in respecting the memory of what came before.”

Boca del Río, Mexico, was not an industrial center. But over time, this once important port city was eclipsed by nearby Veracruz and fell into decline. City leaders are betting the arts can reverse their fortunes, and hope that Michel Rojkind, in Mexico City, will kick-start that process this fall with his tourism-worthy Foro Boca, a jagged assemblage of striated concrete volumes that will house an 800-seat concert hall for the city’s orchestra, and other functions.

Atelier TAG’s 875-seat Gilles-Vigneault Theater in Saint-Jérôme, Quebec, is also a craggy affair — and opens in October with a similar mission: to recast Saint-Jérôme — known for its logging and paper industries — as an arts center that can draw visitors from nearby Montreal, and elsewhere. The theater will anchor a “festival square,” over which it reaches with a dramatically cantilevered, 10,000-square-foot canopy, intended “to encourage gathering and outdoor performance,” according to the Montreal firm’s designers, Katsuhiro Yamazaki, 45, and his partner and wife, Manon Asselin, 50, who won the Prix de Rome architecture prize in 2008.

Image

Nader Tehrani’s Daniels Faculty of Architecture, Landscape, and Design at the University of Toronto.CreditJohn Horner

Ms. Asselin, like many of the leading architects of her generation, teaches as well as practices. So does Nader Tehrani, 53, dean of Cooper Union’s Chanin School of Architecture and co-founder of the Boston practice NADAAA. This fall, Mr. Tehrani will finish something highly unusual: his third building for an architecture school — this time for the Daniels Faculty of Architecture, Landscape, and Design at the University of Toronto. The professional scrutiny that accompanies designing for each other can make an architect squirm, but Mr. Tehrani was game for another run. For Daniels, he floats an origami-like roof over a 110-foot-wide column-free room to create floodlit studio and social spaces below. A new circulation spine attempts to better link the building, which is set on a traffic roundabout, into the city.

Image

Jürgen Mayer H’s Business School for FOM University in Düsseldorf, Germany.CreditDavid Franck

The Berlin architect Jürgen Mayer H, 51, wants his Business School for FOM University in Düsseldorf, Germany, to take on an urban agenda as well. In addition to its classrooms and meeting facilities, FOM offers a series of cantilevered balconies that create gathering spaces overlooking the city and an adjacent park. The biggest of these also attaches to a neighboring viaduct, inviting pedestrians to utilize the building as a pathway down to the park.

Thanks to a percolating economy and the technological revolution that swept through architecture while most of these designers were building their practices, many of them are producing work at speeds and scales that were not possible even a decade ago. Today, a five-person office like the Oyler Wu Collaborative in Los Angeles, founded in 2004, can produce a residential high-rise in a faraway place — even one with the complex, syncopated screens that encase their recently completed Monarch residential tower in Taipei. “The building code there encourages standardization,” said Jenny Wu, 42. Her husband, Dwayne Oyler, 45, added, “We wanted to show that even in a constrained environment, you can still be creative.”

Image

SHoP Architects‘ American Copper Buildings in Manhattan, joined by a bridge that contains a swimming pool.CreditSHoP Architects

Two firms of this generation stand out for the scale and ambition of their enterprises. In New York City, SHoP Architects (whose founding partners range in age from 50 to 54) is now 200 strong, with 19 projects under construction around the world, and a dozen more in design. Two will open this fall in Manhattan. The first, in October, is Pier 17 at the South Street Seaport, reimagined as a 300,000-square-foot retail and entertainment complex. Upstream are the 48- and 43-story American Copper Buildings, sibling apartment towers that look as if they were being pulled toward each other by a 100-foot bridge at their waists (inside of which is what must be the coolest swimming pool in the city). Over time, the copper exteriors will oxidize to a Statue of Liberty green — a slow-motion art project provided by the architects, and by nature.

The youngest architect in this current group also has the largest practice. Bjarke Ingels, 42, started the acronymically perfect Bjarke Ingels Group (BIG) at the ripe old age of 30 and now employs nearly 450 people, primarily in Copenhagen and New York. BIG’s projects are by turns unorthodox, clever and even hopeful. Like the German war machine it in part catalogs, the Tirpitz Museum in Blavand, Denmark, which opened this summer, is an artifact buried in the sand. The Lego House, which opens Sept. 28 in Billund, Denmark, is a hybrid museum and play center devoted to the ubiquitous toys, and is, of course, a mound of interconnected blocks with a roof-scape of primary and secondary colors. But it is the Amager Resource Center in Copenhagen that epitomizes BIG’s approach. When completed in early 2018, the massive waste-to-energy plant will feature a stack that blows harmless vapor smoke rings to indicate tons of conversion, and — yes — a ski slope on its roof.

Mr. Ingels calls his approach ‘‘hedonistic sustainability’’: sustainability that increases the enjoyment of life.